Electron tube



Jan. 6, 1959 c. E, MURDOCK ELECTRON TUBE Filed Jan. 9, 1953 IN VEN TOR. C/ayon E. Mura ck y ATToQN/EY United States Patent ELECTRON TUBE Clayton E. Murdock, Millbrae, Calif., assgnor to Eitel- McCullough, Inc., San Bruno, Calif., a corporation of California Y Application January 9, 1953, Serial No. 330,474

3 Claims. (Cl. B15-5.38)

My `invention relates to electron tubes having cavity resonators and more particularly to tubes of the velocity modulated type, such as klystrons.

The present invention constitutes improvements in an externally tunable type of `klystron such as disclosed in the patent to Norton, etal., No. 2,619,611, issued November 25, 1952, wherein portions of the cavity resonators are sealed of with insulators and comprise part of the evacuated envelope.

It is among the objects of my invention to provide improved cooling means in a tube of the character described, and more particularly to provide means for cooling the drift tube and associated cavity resonators.

Another object is to provide improvements in the construction of the cavity resonators.

A further object is to provide improvements in the collector electrode.

The invention possesses other objects `and features of advantage, some of which, with the foregoing, will be set lforth in the following description of my invention. It is to be understood that -I do not limit myself to this disclosure of speciesl of my invention, as I may adopt variant embodiments thereof within the scope of the claims.

Referring to the drawings:

Figurel is a side elevational view of a tube embodying the improvements of my invention; and

Figure 2 is an axial sectional view of the same.

Figure 3 is an enlarged fragmentary view showing the construction of the cavity resonator.

In greater detail, the drawings show a three-resonator type of klystron, it being understood thatal greater or -fewer number of resonators may be employed in a tube of this kind. The tube illustrated is particularly designed as an amplifier in the U. H. F. region and having a power rating of several kilowatts C. W. Figures land 2 show the evacuated tube per se apart from the external structure. In the final use of such a tube suitable external resonators are applied as described in the above mentioned patent, one of such external resonators being indicated by the dotted lines 1 in Figure l.

My tube comprises an elongated generally cylindrical envelope having an electron gun 2 at one end and a collector electrode 3 at the other end. 'The electron beam from the gun'to'the collector passes through a drift tube made up of metal sections 4, 6, 7 and 8 extending axially of the envelope and having gaps 9, 11'y and 12 therebetween. Such gaps are bridged by cavity resonator structures forming portions of the tube envelope and generally designated at 13, 14 Vand 16.

Electron gun 2 includes a disk-shaped cathode 17 and a surrounding focusing electrode 18, the cathode being heated by a filament 19, all of which is supported by a glass stern 21 forming an end of the evacuated envelope. Cathode 17 is preferably of a material such as tantalum heated by electron bombardment from the filament, all in accordance with conventional practice.

The electron gun is housed in a cup-shaped metal sec- 'ice i. prises a hollow metal member 24 supported from a diskshaped metal section 26 of the envelope. A glass en-l velope section 27 sealed between flanges 28 provides a supporting connection between the collector member 24 and the envelope section 26. An aperture 29 in metal piece 26 is aligned with the collector electrode and is coaxial with the drift tube. The metal disk 26 is of iron and also functions as a pole piece for the external focusing magnet.

With the above described structure an electron beam from gun 2 is accelerated by a positive potential on anode 22 and passes through the drift tube, past the interaction spaces provided by gaps 9, 11 and 12, and finally terminates on collector electrode 3, the beam being directed down the drift tube by an external magnet associated with iron pole pieces 22 and 26. The three-cavity resonators 13, 14 and 16 coacting with the interaction spaces at gaps 9, 11 and 12 serve as the frequency determining elements of the device.l In the tube illustrated, which functions as an amplifier, the input signal for modulating the electron stream is fed into the first resonator 13, and the radio-frequency output is taken from the third resonator 16, in accordance with the usual manner for threecavity type klystrons.

As previously mentioned herein, the particular kind of -tube shown is adapted for external tuning by the use of suitable external resonators, one of which is indicated by the dotted lines 1 in Figure 1. The use of such external resonators for tuning over a wide band of frequenciesis possible, of course, because of the sealed-off nature of the resonators 13, 14 and 16 which comprise part ofthe evacuated envelope.

kContinuing with the description of Figures l and 2, drift tube end section 4 is brazed to anode piece 22, and the other end section 8 is brazed to piece 26. The inter'- mediate sections 6 and 7 of the d rift tube are axially aligned with the end sections 4 and 8, these several sections forming parts of the side Walls of the evacuated envelope. Circularl resonators 13, 14 and 16, which are disposed transversely of the envelope axis, are mounted on the drift tube sections and form additional side wall portions of the evacuated envelope. In other words, the resonator vstructures provide vacuum-tight walls bridging the gaps between the drift tube sections.

Input resonator 13 comprises parallel disk-shaped metal end Walls 31 and 32 brazed to the drift tube sections process and then brazing the metalized ends to the metal parts with silver solder or the like.

An important feature of my invention resides in the resonator construction at the flanges 34. Since the ceramic materials have a lower coeliicient of thermal expansion than metals of good electrical conductivity, such as copper, it is desirable to make the flanges 34 of U-shape to provide folded back inner lips 36 connected to the ceramic. This provides a good mechanical ari rangement and also suicient flexibility in the structure i l3.8 projecting from` the end walls to abut the ends of the ceramic. These rings prevent the ilexible flanges. from collapsing when the tube is evacuated, see Figure 3. The intermediate resonator 14 `is of similar construction, having end walls 39 and 41 with a ceramic cylinder 42; output resonator 16 is of like construction, having end walls 43 and v44 with a ceramic cylinder 46. In each of thethree resonators the circular end walls have outer edges providing terminalswith' which suitable contact 'fingers on .the external structures rnay be engaged.

Other important features of my tube structure have to do with cooling the drift tube and associated parts, such cooling being of special importance in a power tube of this kind where one vis dealing with kilowatts of power. As best shown in Figure 2, metal sleeves 47 and 48 are provided about the drift tube sections 6 and 7, sleeve 47 being brazed between resonator walls 32 and 39 and sleeve 48 being brazed between walls 41 and 43. These sleeves are spaced from the drift tube sections to provide water jackets, suitable inlet and outlet connections 49 being provided so that water can be circulated through the jackets. Such structure is very effective because the ends of the resonators as well as the drift tube sections are adequately cooled. Another important feature of this structure is that the sleeves 47 and 4S also serve as reinforcing'members to provide additional strength axially of the tube, which is of considerable importance in a tube of this kind where appreciable length and massivefparts are involved.

Cooling means are also provided for the pole pieces 22 and 26 and the adjacent drift tube sections and resonator walls. As seen at the cathode end of the tube, a sleeve 51 is disposed about drift tube section 4 and is brazed between the pole piece 22 and the resonator wall 31, thus providing a water jacket for those parts. Water connections are made by the ducts 52 at the outer end of the pole piece communicating with the water jacket via passages 53. A like arrangement is incorporated at the opposite end of the envelope by means of the jacket sleeve 54, ducts S6 and passages 57 in pole piece 26. Such structures provide adequate cooling for the pole pieces and associated drift tube sections, as well as the adjacent end walls of the resonators. 54 also serve as reinforcing struts at these points.

Another feature of my structure, having to do with the power handling capabilities of the tube, concerns the collector electrode 3. Referring again to Figure 2, it

will be seen that the collector 3 comprises a hollow cup-shaped member 24 disposed axially ofthe tube. This Ais a drawn-piece,rpreferably of copper. In order to avoid spot heating by the beam being focused on the end of the member 24, I provide an insert 58, also of copper, having a tapered bore 59 extending axially of the drift tube. This structure spreads the impinging electrons along the length of the electrode and also provides uniform conduction of heat to the outer surface of cup 24. The cooler for the collector member 24 comprises a water jacket 61, with inlet and outlet ducts 62 and-63, and having 4an inner tubular deilector 64 for directing the inlet Water along the sides of the electrode in parallelism with the bore 59. With this construction, even though high Sleeves 51 and energy electron beams are employed, I have dissipated many kilowatts of'power Without difculty.

The exhaust tubulation for the envelope is also incorporated in the collector electrode structure. As shown, the bore 59 continues through the insert 58 and communicates with a metal tubulation 60 brazed to the end of cup 24. After evacuation :of-.the envelope this tubulation is pinched otfat tip 65.

I claim:

l.v A cavity resonator ,type 'electron tube, comprising an elongated evacuated envelope,-:an electron gun at one end of the envelope and a collector electrode at the other end, a drift .tube extendingA axially of the envelope, said collector comprising a cup-shaped metal member forming a portion of said l,evacuated envelope, and a metal insert in the member having a Wall thickness substantially :greater than that of the member and having a tapered bore axially aligned with the drift tube, the external surface of said insert and the inner surface of said member being in contact over a 'substantial area, whereby heat is rapidly and uniformly transmitted from said insert to said member.

2. A cavity resonatory type electron tube comprising an elongated evacuated-envelope, an electron gun at one end of the envelope and a collector electrode at the other end, a drift'tube extending axially of the-envelope and forming side Walls of the evacuated envelope, said drift tube comprising spaced 'sections with a gapk therebetween, a cavity resonator disposed'transversely ofthe envelope axis adjacent the gap, said resonator comprising metal-end'walls mounted on adjacent drifttube Asections and extendingoutwardly from said sections, acylinder of insulating material'yhaving Va diameter larger than that of the drift tube interposed between the end walls, vacuum-tight joints at the ends of the cylinder comprising thin metal sealing anges connectedfbetween the end walls and the insulating cylinder., and'abutments von the end walls engaging the ends of the vinsulating cylinder to take the axial thrust between the Aend walls and said cylinder.

3. A cavity resonator type electron tube, comprising an elongated evacuated envelope, an electron gun at one end of the envelope and a collect-or electrode at the other end, a drift Vtubeextending axially of the envelope and forming side walls of the evacuated envelope, said `drift tube comprising spaced sections with gaps therebetween, a plurality of cavity resonators disposed transversely of the envelope axis at the gaps, said resonators comprising metal end walls mounted on adjacent drift tube Isections and extending outwardly from said sections, cylinders of insulating material having diameters larger ,than that of the drift tube sealed between said walls and Vproviding vacuum-tight walls across the gaps, and a metal sleeve of *larger diameter than the drift tube extending between and connected to the end walls of adjacent resonators providing a reinforcingmember to maintain alignment of the drift tube sections axially ofthe envelope.

References Cited inthe file of this patent UNITED STATES PATENTS Re. 21,163 v Rose July 25, 1939 1,181,440 E dgecomb Ma'y 2 1916 2,238,619 Berkey Apr. 15, 1941 2,529,668 Wangv 'N oV; 14, ,1950 2,619,611 Norton 'et al. Nov. 25', 1952 2,629,066 Eitel et al Feb. 17,1953 2,632,863 Norton Mar. 24, .1953 

